Disc drives are used for data storage in modem electronic products ranging from digital cameras to computers and network systems. Typically, a disc drive includes a mechanical portion, or head disc assembly, and electronics in the form of a printed circuit board assembly mounted to an outer surface of the head disc assembly. The printed circuit board assembly controls functions of the head disc assembly and provides a communication interface between the disc drive and a host being serviced by the disc drive.
Typically, the head-disc assembly has a disc with a recording surface rotated at a constant speed by a spindle motor assembly and an actuator assembly positionably controlled by a closed loop servo system. The actuator assembly supports a read/write head that writes data to and reads data from the recording surface. Disc drives using magneto resistive read/write heads typically use an inductive element, or writer, to write data to information tracks of the recording surface and a magneto resistive element, or reader, to read data from the information tracks during drive operations.
The disc drive market continues to place pressure on the industry for disc drives with increased capacity at a lower cost per megabyte and higher rates of data throughput.
As improvements continue to propagate and new functionalities are introduced into disc drives, the cost of the electronics used in supporting those improvements and newly introduced functionalities emerges as a concern for maintaining a competitive posture in the marketplace. Typically, as part of the electronics supporting the functions of a disc drive, a disc drive is likely to include a microprocessor based controller, a pre-amplifier, host to drive interface electronics, analog to digital converts, a read/write channel and an application specific integrated circuit (ASIC) based servo controller.
In prior disc drives, communication between the read/write heads and either the servo ASIC or the microprocessor-based controller is typically supported by a number of serial ports communicating with the read/write channel. In a typical drive, a servo ASIC is configured with dual serial ports, one port for handling servo data and the other for handling read/write data. In such instances, the microprocessor-based controller typically communicates directly with the servo ASIC, and the servo ASIC manages the functions of the serial ports.
A primary cost component of the electronics of a disc drive is the servo ASIC device, and pin count of the servo ASIC has a direct relationship to the overall cost of the device. As such, challenges remain and a need persists for a reduction in the actual pin count of the servo ASIC, or an effective reduction in servo ASIC pin count. An actual reduction in pin count provides a direct cost reduction for a disc drive, while an effective reduction in pin count fosters the support of additional functionality absent a cost increase in the electronics to support the additional functionality. It is to this and other features and advantages set forth herein that embodiments of the present invention are directed.